Method and apparatus for perforating sheet material



6 Sheets-Sheet 1 l. H. wlLSEY ETAL Filed May 12, 1941 Sept. 18, 1945.

METHOD AND APPARATUS EOE PERFOEATING SHEET MATERIAL @RW mv A. OR

l. H. wlLsEY ErAL Sept. 1s, 1945.

METHOD AND APPARATUS FOR PERFORATING SHEET MATERIAL Filed May 12, 1941 6 Sheets-Sheet 2 Sept. 18, 1945. l. H. wlLsEY ETAL METHOD AND APARATUS FOR PERFORATING SHEET MATERIAL Filed May l2, 1941 6 Sheets-Sheet 3 Sept. 18, 1945. l. H. wlLsEY ETAL 2,385,246

METHOD AND APPARATUS FOR PERFORTING SHEET MATERIAL Filed May l2, 1941 6 Sheets-Sheet 4 Sept. 18, 1945. l. H. wlLsEY ETAL METHOD AND APPARATUS FOR PERFORATING SHEET MATERIAL Filed May 12, 1941 6 Sheets-Sheet 5 0 Ufff/6,5

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METHOD AND APPARATUS FOR PERFORATING SHEET MATERIAL Filed May 12, 1941 6 Sheets-Sheet 6 Patented Sept. 18, 1945 METHOD AND APPARATUS FOR PERFORAT- ING SHEET MATERIAL Irven H. Wiisey and Arthur E. Neumann, Chicago, Ill.; said Neumann assigner to said Wiisey; Ruth Ann Wilsey exeoutrix of said Irven H.

VVilsey, deceased Application May 122, 1941, serial No. 393,134

(ci. 11s- 265) 22 Claims.

The present invention relates to a novel method and apparatus for perforating sheet material and more particularly to pattern perforating such material.

The invention may be utilized in perforating a large variety of sheet materials and other articles including, for example, such dissimilar items as paper, veneer, felt and leather. The type of perforations contemplated are so small as to be nearly, if not completely, invisible to the naked eye, the perforations having a diameter of the order of 0.020 to 0.0005 inch. Sheet materials having such extremely fine perforations have been found to have large and varied fields of use. For instance, in packaging cement, flour and other such finely divided materials in valve type paper bags it is of great importance that the bag be able to fbreatheJ In other words, its wall structure should have sufllcient porosity to permit the egress of air displaced by the contents of the bag as it is filled, and yet the wall structure must not permit the finely powdered contents to filter through. Lack of porosity causes flour or similar material to fluff along the side of the bag during filling and is a serious matter in valved bags. For a porous bag for such materials several factors must be carefully controlled, viz: the size of holes or perforations. the uniformity of their distribution over the sheet and the density of their distribution` Not only must these factors be controlled but in many instances should be varied to accommodate different materials.

One primary object of the invention is to provide a novel method and apparatus for pattern perforating sheet material. By pattern perforating is meant the aperturing or puncturing of the sheet in such manner that a preselected relative spacing and alinement of the perforations per unit area on the sheet are attained. This does not mean that the layout of holesy in each unit area is an exact duplicate of that in every other area but is to be distinguished from a mere random perforating of a sheet in which the perforations fail at irregular points and the average density or number of perforations per unit area is permitted to vary.

A more specific object of the invention is to provide a novel method and apparatus for pattern perforating a sheet through the use of periodic electric arc discharges between a pair of electrodes at opposite faces of the sheet, in which the sheet and the electrodes are moved continuously relative to each other, and the perforation spacing controlled by varying the relative speed of movement between the sheet and electrodes, or the periodicity o! the discharges, or both.

Another object is to provide a sheet perforating machine utilizing electrical arc discharges for forming the perforations, which machine is of such character that it can be readily controlled by cutting in or out various sections to accommodate traveling sheets or webs of dierent widths.

Another object is to provide a'machine for perforating a traveling sheet or web by electrical arc discharges, in which the discharges are effected between successive points along crisscrossing lines over the face of the web and in which a novel arrangement is provided for varying the number of such lines from which the discharges take place so as to vary correspondingly the density of the perforation pattern.

Still another object is to provide an arc discharge type `perforating machine for a traveling web or sheet embodying a novel arrangement for preventing burning of the sheet in the event of undue diminution in the speed of, or stopping of, the web advance.

A further object of the invention is to provide a machine for perforating a web by electrical arc discharges which embodies a novel arrangement for variably controlling the size of the perforations formed in the sheet.

The invention also resides in the provision in the machine of various other novel features including its sectionalized control, operation-condition indicating mechanism, and electrode structure.

Further objects and advantages of the invention will become apparent as the following description proceeds, taken in connection with the accompanying drawings in which:

Figure 1 is a side elevation of a sheet material perforating machine embodying the invention and adapted to carry out the novel method herein disclosed.

Fig. 2 is a plan view of the machine.

Fig. 3 is an end elevation of the machine, taken from the right hand end as viewed in Fig. 1.

Fig. 4 is a transverse sectional view taken substantially along the line 4--4 in Fig 1.

Fig. 5 is an enlarged, fragmentary transverse sectional view taken substantially along the line 5-5 ln Fig. 2.

Fig. 6 is an enlarged detail view of one of the electrode rolls.

Figs. 7 and 8 are respectively longitudinal and transverse sectional views of the roll shown in Fig. 6.

vspirit and scope oi' the Fig. 9 is a detail perspective view of a portion of one of the electrodes for the roll.

Fig. 10 is a detail perspective view of an insulating segment for the roll.

Figs. 11, 12 and 13 are diagrammatic views showing, respectively, various distributions ci the zigzag electrodes over a unit area oi' sheet material.

Fig. 14 is a generally diagrammatic plan view of the machine showing the circuit connections for the top set of electrode rolls.

Figs. 15 and 16 are diagrammatic views illustrating the use of the sectionalized circuit connections for the electrode rolls.

Figs'. 17 and 18| are respectively side elevation and plan views of a speed responsive switch mechanism used in the control circuit for the machine.

Fig. 19 is a wiring diagram for the machine.

Fig. 20 is a wiring diagram of a modliled form of electrode supply circuit.

While the invention is susceptible of various modications and alternative constructions, I have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understood that I do not thereby intend to limit the invention to the specific i'orm disclosed, but intend to cover all modifications and alternative constructions falling within the invention as expressed in the appended claims,

In the instant exempliilcation of the invention, the preferred procedure used includes, in brief, the following: A continuous relative movement is effected between a sheet of material. which is to be perforated. and a pair of electrodes between which it is led. Electrical arc discharges are periodically passed between the electrodes and through the sheet to perforate the latter. By controlling the periodicity of the discharges, as well as the speed land path of the relative movement noted, the relative location and spacing of the peri'orations are controlled. To obtain a distributed or over-al1 pattern oi' perforations on the sheet, the discharges are, in the present instance, made at spaced rDiiied Bets of rolls Il, Il

I2 and Il, paralleling the center roll and arranged on diametrically opposite sid o! it. Hence, if a suiilcient dinerence in potential is established between the two side rolls i2 and ilanarcdischargewilltakeplaceinthegaps al and a: (see Fig. 5), the center roll constituting a common or cross-over electrode for eachoitheseriesarce. Byleadingtheweb il up through the gap an over the top of the center roll Ii and down through the gap ai. it is punctured at spaced points by the two simultaneous series arcs in the air gaps m and as.

The other two sets o! electrode rolls are substantially identical with the top set il, i2, il, described above and each of them is also arranged to form two air gaps for series arcs. Thus, the intermediate set of rolls comprises a center roll i i* and side rolls I2* and Il* while the lower set includes a center rolls Il" and side rolls i2lb and Il (Figs. 3 and 4). The entering web il is led upward from the bottom of the machine (Fig. 1) successively between the opand il, I!l and li, i2 (Fig. 3), then over the top of the upper center `roll il and nnally down through the successive pairs oi' opposed rolls Il, il and Ii, and lib, ill. In this way the web passes successively through six air gaps between opposed pairs of rolls, and through each of which gaps arc esmaybepassedtopuncturethe advancing web. Suitable guide rolls (not shown) located beneath the electrode rolls exert a downward tension on the portions o! the web ill extending down from each side of the top center roll Ii so that the web i'rictionally engages this roll. entLv, the web is advanced by rotation oi' this roll Ii and in substantial synchronism with it.

points along intersecting zigzag lines overlapping each other in staggered and oirset relation. By varying the number of such overlapping zigzags along which the discharges take place the density of the pattern is correspondingly changed. Though the relativen motion of the sheet and electrodes, etc., set forth above can =be eected by hand, the great number of perforations required makes the use of an automatic machine highly desirable in carrying out the disclosed method. A more complete understanding of the method itself will be had from the succeeding description of the machine and its operation, the machine disclosed being especially adapted to carry out the method contemplated.

In the instant machine (Figs. 1 and 2) a web or sheet i0, of material to be perforated is, in general, led between a series of opposed rolls which are, in the illustrated machine, driven in synchronism with the speed o! web advance. On the peripheries of these rolls are suitableelectrodes, hereinafter described, and electrical arc discharges or sparks jumping between the electrodes on opposed pairs o! the rolls puncture the advancing web. In the illustrative construction these electrode rolls are arranged in three superimposed sets of three. The top set (Fig. 2) comprises a center roll ii and two side rolls which is being perforated.

The nine electrode rolls identiiied above are rotatably Journaled in a suitable framework oi generally rectangular form. It comprises (Fig. 1) a pair oftransverse bed channels il Joined by lower longitudinal members il. Parallelling the members il* are upper longitudinal frame members il* Joined to each other and to the members I Il by, respectively, top and side X-frames il. At each end oi.' the framework described are ilxed upper and lower horisontal plates I1 and il. Between these opposed pairs of plates are, in each case, three upright brackets i8, i3 and 2l journaled the vertically alined groups of rolls ii, ii, iih and i2, III, i2 and il, il, Il. Each oi' these brackets Il, II and 2l comprises a vertical plate with a corresponding web il, I9l and 2l* on its inner face apertured to receive the bearings for the rolls.

To adjust the lateralepacing of the rolls in each set, and thus correspondingly vary the air gaps between them, horizontal adjustment screws 2| and 22 (Fig. 3) are arranged in registering holes in the webs il, Il' and 20. The central web Il* is gripped between pairs ci' clamping nuts 23 on the screws 2i and 22 while the webs II* and 2|- are, respectively, grippedbetween pairs ot nuts 24 and 2l. By threading the nuts Il and 25 along the screws Il and nfthe outer brackets i! andV 2l are moved toward and away from the center bracket Il and the air gap spacing between the laterally alined rolls thus adjusted. This spacing is ordinarily of the order o! magnitude of about three times the thickness o! the sheet In general, the spacing is such that the sheet or web Il does not completely nll the gap between the opposed rolls (Fig. 3) in which are respectively utilized .(Fig. 3).

asma-io adjustment operation described, and to hold them nrxnly in adjusted position, cap screws 23 are A pair of these cap screws passes through corresponding slots in a '.oot on each end of each of the brackets and is threaded In corresponding holes in one of the plates I or I1. By loosening these cap screws the brackets are freed for transverse adjustment and after the desired adjustment has been eiiected the cap screws are retightened to hold the roll-supporting brackets fixedly in position.

The vertical spacing of the rolls is not lparticularly critical and no provision is made for its adjustment. It is great enough to permit the insertion of an operators hand, in threading a new web or sheet into the machine, and to prevent arcin-g between vertically alined rolls. It is, however, small enough to insurel compactnessfor the machine.

In order to rotate all of the nine electrode rolls in unison a common or interconnected drive system is used for them. In the present instance power is applied through the projecting end of the center roll IIn (Figs. 1v and 2). On the opposite end of this roll is av sprocket 21 (Fig. 3) over which is led an endless roller chain 28, which also passes over sprockets 23, 30, 3| and 32, fixed respectively on the rolls I2, I3, Izb and |31. To drive the remaining rolls II, I2, I3 and II, additional endless roller chains 33, 34, 35 and 35 are utilized (Fig. 4). The chain 33 is led over sprockets 31 and 35 fixed on the rolls I2 and I2". Similarly, the chain 35 is led over sprockets 33 and 40 ilxed on the rolls I3 and I3a while the chains 34 and 35 mesh respectively with a pair of sprockets 4I on the roll II and with sprockets 42 and 43 on the rolls II and Il". The arrows in Figs. 4 and 5 indicate the direction of roll rotation. In the event that the machine is being used, for example, to perforate paper, the primary drive roll Il* may be driven from the same unified drive system which also operates a slitter located ahead -of the perforator and a reroll mechanism following it. The high speed with which the webv I0 may pass through the present perforator at. for example, several feet .per second, makes it possible to use the perforator in any ordinary line-up of paper making or handling machines without the necessity of slowing down the line because of the presence of the perforator.

Turning now to the details of the electrode structures of the various rolls, the center, or what might be termed the cross-over rolls, I I, I I and IIb are provided with electrodes in the form of simple annular metal bands 44, 44, 44b`to 44h.

These electrode bands may be made of copper or other suitably electrically conductive material. Each of them completely encircles the roll on which it is mounted and is fixed on the periphery of a sheath or cylinder 45 of insulating material. This sheath 45 is, in turn, telescoped on and fixed to a hollow steel shaft 45. Each of the center rolls II, II and II" is identical in construction except that the sets of electrode bandsJ on them are oti'set longitudinally with respect to each other, for a purpose which will hereinafter appear. The amount of this longitudinal oiiset is the same as that shown for the zigzag electrodes on the side rolls and which is indicated in Fig. l.

By spacing the electrode bands 44. 44 to 44'I (Fig. 2) laterally from each other along the supporting insulator sheath 45 they are eifectually insulated from each other, In this way they form a series of separate and electrically insulated electrodes so that arc discharges can be passed to them from similarly spaced electrodes on the side rolls, thereby making possible a corresponding number of arc discharges through the web I0 at laterally spaced points in the latter.

On the outer or side rolls I2, I2", I2", I3. I3, and I3b a plurality (nine in the present instance) of electrodes areprovided at spaced points along each of the rolls and in position to cooperate with the band electrodes on the center rolls I I, I I'L and I Ib. In the case of the roll I2 the separate electrodes on it have been identified as 41, 41 to 41h. those on the roll I2*i as 48, 43 to 43h, those on the roll I2b as 49, 49 to'43h, those on roll I3 as 50, 5IiI to 50h, those on roll I3n as 5I. 5I* to 5I, those on roll I3h as 52, 52'l to 52h (Figs. 1, 2 and 15). Each of the electrodes is identical and, accordingly, a description of electrode 41 on roll I2 will serve for all. This electrode (Fig. 6) is of zigzag or wavy form and comprises a bar 53 (see also Fig. 9) of nichrome steel, or other electrically conducting material, bent i7. zigzag form as shown and with its ends jointed together to form a complete annulus encircling the roll.

The electrode bar 53 has feet 54 bent laterally from its lower edge and projecting alternately in opposed directions (Fig. 9) which rest on a sheath or cylinder 55 of insulating material (Figs. 'I and 8). Segments 56 of insulating material (Fig. l0) are inserted between the bends in the electrode bar 53 (Fig. 6) and overlie the feet 54, these segments being screwed to the sheath 55 so as to hold the bar 53 in place. The insulating sheath 55 is telescoped on an inner insulating sheath 51 which is longitudinally slotted (Fig. 8) to receive, and insulate from each other, interconnecting conductors between various ones of the zigzag electrodes. This inner sheath 51 is in tum telescoped over and fixed to a hollow steel shaft 53. Suitable annular insulating spacers 53 (Figs. 6 and 7) encircle the sheath 55 between the annular rows of segments 55.

It will be observed that as the rolls II and I2 (Figs. 2 and 5) rotate with respect to each other in the directions indicated by the arrows in Fig. 5, the point of least distance, in the air gap g1 between the band electrode 44 on the roll II and the zigzag electrode 41, moves progressively along the latter electrode. When a potential is created between the electrodes 44 and 41 so that an arc discharge passes between them-it will, in general, .lump between the most closely adjacent points on them. Consequently, a periodically applied voltage between the electrodes 44 and 41 will cause a series of discharges between them at successively spaced points along the zigzagelectrode 41. The spacing along the electrode of successive ones of these discharges will depend Aupon the relation between the periodicity of the discharges and the speed of rotation of the zigzag electrode. As is hereinafter explained in greater detail, advantage is taken of this characteristic to control the spacing of the arc-formed perforations in the traveling web I5.

To obtain a generally uniform or controlled patterned distribution of the perforations over the web I5 a particular geometric relation of the various zigzag electrodes, under which each portion of the web passes, is desirably used. For this purpose each of the zigzag electrodes on the trodes on the side rolls I2, I2* and I2 is angularly offset with respect to the corresponding electrode on the next adjacent side roll. On the other side of the machine, the zigzag electrodes on the rolls I3, I3* and I3b are offset with respect to each l other by the same amount as those in the rolls I2, I2* and I2". Thus the electrodes on the roll Il are directly across from those on the roll I2, those on roll I3* directly across from those on I2", etc. Also, the electrodes on the rolls I3. Il* and IIb are staggered angularly about their respective rolls, but in this case they are staggered not only with respect to each other but with respect to the electrodes on the rolls I2, I2* and I2".

The details of the above geometric relation of the several zigzag electrodes will be clear upon reference to the diagrammatic illustration in Fig. 11. This figure shows a. portion of the yweb I with criss-cross lines superimposed on it corresponding to the relative positions of the portions of certain of the electrodes on the rolls II,

- Il* and I3 which the web passes successively in the order named as it moves down through the machine. The particular portion of the web chosen for illustration passes by portions of the electrodes 50*, 5I* and 52* on the rolls I3, I2* and I3, respectively. The developed outline of the electrode II* has been shown in full lines, that of the electrode 50* in dash lines, and that of the electrode 52* in dot-dash lines, in order to distinguish them. The staggered and oifset relation of these three electrodes, which is typical for all of those on the rolls I l, I3* and Hb, will be apparent from this development of them in Fig. 11.

This same portion of the web Il also passes up through the three gaps on the other side of the machine, or, in other words, past the rolls I2, I2* and I2 in that order and, hence, successively under the electrodes 48", 4l* and 41*. 'I'hese have been indicated in Fig. 12 by, respectively dotted lines, dash double-dot lines and light full lines. Thus, Fig. 12 shows the full pattern of distribution for the various zigzag electrodes as they successively overlie a single unitary portion of the web. The arc discharges, heretofore referred to, take place at successively spaced points'along each of the intersecting lines so that the entire surface of the web is finally covered with closely spaced, though fairly accurately distributed, perforations. By cutting into or out of circuit certain of the zigzag electrodes which pass over a particular portion of the web, the number of perforations can be varied, although the uniformity of the pattern of the perforations is maintained. For example, in Fig. 13, the lines for the electrodes 41* and 50* have been shown simply in light lines (compared to the contrasting heavier lines for those same electrodes shown in Fig. l2) so as to indicate that these electrodes are deenergized. In such case the perforation-forming arc discharges will take place at spaced points along only the heavier lines indicated for the electrodes 52, II", 49* and 48*. Accordingly, homogeneity or uniformity of perforation distribution is maintained, although the density of perforation per unit area of the web is substantially diminished.

Various other ones of the electrodes may be out into or out of circuit, by a switch mechanism subsequently described, to effect other variations in the pattern of distribution.

Similarly, but cutting into or out of circuit various ones of the zigzag electrodes along each of the rolls, the machinel can be conditioned to accommodate, with maximum efficiency, sheets or webs of different widths. Thus, upon reference to Fig. 15 it will be observed that in the right hand vertical bank of rolls I2, I2* and I2 only the electrodes 411, 41K 41h and 48. 48, 48h and 48', 4v, 48h are energized (as indicated by the heavier lines in which these electrodes are drawn) Similarly, in the left hand bank of rolls Il, I I* and Il only the corresponding three end electrodes, shown in heavy lines, are energized. The machine is in such case conditioned to receive a web having a lateral width equal to not more than the length oi' roll covered by three electrodes on each side roll. For wider sheets successive groups of the electrodes along each roll may be energized.

Even when the machine is set up for a narrow web the density of perforation distribution can still be controlled as described. Thus, upon reference to Fig. 16, for example, it will be seen that only the end group of electrodes is energized so as to accommodate a narrow web (as described above in connection with Fig. 15) but among even these end electrodes those on the rolls I2* and I3* are, in this instance (Fig. 16), deenergized so as to cut down the number of perforations per unit area as previously described.

In order to make it possible to cut into or out of circuit different electrodes for the various purposes set forth above, a sectionalized type of cir- Acuit is used for applying potential to the electrodes. Upon reference to the illustrative construction in Fig. 14 it will be seen that the electrodes on the roll. I2 are wired in three successive groups, each group containing three adjacent electrodes. In each of these groups two of the electrodes are interconnected. Thus, in the right hand group, comprising electrodes 411, 41' and 41h, the electrodes 41t and 41l are interconnected by a conductor C0. Similarly, in the middle group the pair of electrodes 41 and 41d are interconnected by conductor 8|, and in the left end group the electrodes 41 and 41* are interconnected by a conductor 62.

On the opposite side of the machine, that is, on roll I3, the electrodes are wired in similar circuit groups or sections and in each of these groups of three, two of the electrodes are interconnected. Speciilcally, the electrodes 50' and il are interconnected by a conductor 63, the electrodes IIN and 50 by a conductor R4, andthe electrodes 50* and l0" by a conductor 6B. On this roll I3 the electrodes are connected by a common supply lead I8 to a slip ring 41. On the other roll I2 however, three separate slip rings and 10 are connected to corresponding ones ot the electrodes in the three sections or groups by conductors 1 I, 12 and 12.

With the circuit connections described above. when potential is applied between the slip rings Gl and 81 current will flow through a circuit Upon tracing this circuit in Fig. 14 it will be seen that it includes a total of six air gaps in each of which an arc discharge must take place to complete the circuit. Specifically, the circuit,

assume of electrodes on the rolls l2, Il' (Fig. 14) a p0- In the same way, when a potential difference is established between the sli a circuit is completed throus Identical sectionalized energizing circuits are provided for the rolls I2, I3* and I2", Il In the I middle and lower sets, respectively, as indicated in Figs. 15 and 16. As terminals for these circuits on the rolls I2l and lI2, respectively, are provided sets of three slip rings each, viz: 14, 1I, 18 and 11, 18 and 18. On each of the rolls II and ilh is provided a single slip ring 88 and 88, respectively.

As a means of applying potential to the various sections of the electrode circuits set forth above, a high frequency generator 8| is utilized (Fig. 19). 'I'his generator is, in general, of conventional form and comprises an armature 82 and a separately excited field 88, which is connected to suitable direct current supply lines L1 and In. The generator armature 82 is driven by a variable speed motor 84 having an amature 8l connected to alternating current supply lines In and Lr. as well as a separately excited eld 88, connected to a suitable source of current through a speed adjusting rheostat 81.

To the output leads 88, 88 of the high frequency generator 8| are connected, in parallel relation to each other, a plurality of step-up transformers, one for each of the electrode sections heretofore described or, in other words, nine in number for the present machine. Each of these transformers has one of its output terminals connected to a corresponding one of the slip rings on one of the rolls I2, I2IIL or i2b and its other terminal connected to a corresponding return slip ring on one of the opposite rolls I3, I8* or Il. tical, and are each connected in parallel to each other in the same'manner to the output leads of the generator, only one has been shown, namely, thevtransformer 88 (Fig. 19) for the slip rings 88 and 81 (see Fig. 14). 'I'his transformer is of the high-reactance current-limiting type and includes a primary winding 8| inductively coupled 'with a sectionalized secondary winding including sections 82 and 88. One terminal of each of these secondary windings is grounded and the others are connected, respectively, through conductors 88 and 88, with brushes 81* and 88 for the slip rings 81 and 88 (see also Figs. 5 and 14) It will be observed upon reference to Fig. 5 that the brushes are of conventional form, being resiliently mounted in insulating panels 88 and 81 secured to opposite sides of the machine framework. As indicated in Figs. 1 and 2 the corresponding brushes for all of the slip rings are mounted on these same panels.

The generator 8| (Fig. 19) may, for example,

rings 18 and 81l Since these transformers are idenhave a rated output of 2500 cycles at 110 volts. The frequency of its output potential is of course a function of the generator speed and can be controlled by changing the speed of the variable speed driving motor 88, through the medium of the speed controlling rheostat 81. In such case the transformer 88 may be wound to step up the voltage to 10,000 volts or whatever is required to produce an arc discharge of desired intenslty through the six series gaps in the electrode section which the transformer. supplies. When operating at 2500 cycles, two discharges take place for each cycle, that is, one on the positive peak and one on the negative peak. Hence there are 5000 discharges per second but since there are six gaps in each electrode section .there will be 30,000 separate arcs in each section per second or 30,000 perforations formed per second in the portion of the web through the section. There are, however. nine electrode sections in the machine shown, so ythat when all are operating, there will be 270,000 perforations formed per second or 16,200,000 per minute. Despite this tremendous speed with which the perforations are formed, their distribution pattern over the web is accurately controlled by the elec trode arrangement heretofore described.

To initiate operation of the machine, after the generator 8| has been started, the operator closes the manual on-oif switch |88 (Fig. 19) which, together with a safety switch |8| hereinafter described. connects the actuaing winding of a relay winding |82 to suitable supply lines Ls and Ls. Thereupon this relay closes its normalhr open contacts |88, which are interposed in the conductor 88 leading to the transformer primary winding 8|. Also interposed in this conductor 88 is an individual manually operated on-otr switch |84, one of which is provided vfor each of the transformers. By closing and opening selected ones of these individual on-oil switches, the associated transformers can be cut into or out of lcircuit to condition the desired number of electrode sections for operation. Each of the transformers is protected by a pair of yfuses in its input leads. When the relay |82 drops out, due to the opening of the manual on-oiI switch |88, or of the safety switch III, all of the transformers are simultaneously disconnected from the generator 8|.

The physical character of thev hole or puncture formed in thel sheet by an arc discharge depends to some extent upon the power of the discharge or in other words upon the product of the in-phase current and voltage. As the power is increased from a point just sumcient to eifect puncturing a sheet, thel size of the puncture or perforation increases in more or less direct proportion. In the event that paper is being perfo'- rated, it has been found by microscopic examination of the sheets that the marginal edges of the perforations are made up of fused material. When perforations. with fused edges, are formed in even cheap rosin content mapping paper it has been found that the strength of the paper has not been materially decreased but in many instances actually increased.4 This-increase may be due to various causes, probably including the fusion of the edges of the perforations. As the power of the arc discharge is still further increased, from a point at which a fusededge perforation is formed, vsome charting at the edges of-the stilllarger perforations appears.

Such charring is, 1in many instances, undesirable for various reasons in that it interferes with subsequent printing on the sheet surface and may, if carried far enough, structurally weaken it. It will thus be clear that accurate control of power of the discharges is very desirable. Even aside from the difference in character of the perforations formed there are other reasons for controlling their size. For example the particular use to which the sheet material is to be put will frequently govern the maximum or minimum sise of perforation which is desired or even permissible.

The illustrative machine comprises two distinct means for controlling the size of the perforations formed in the web Il. First. means is provided for controlling the output voltage of the generator li, and by means of whichthe power is correspondingly controlled. Second, means is provided for controlling the phase relation of the voltage and current.supplied by the y gneerator Il and correspondingly the product of the in-phase voltage and current, or in other words, the power.

To, control the output voltage of the generator 8l, a rheostat ill is connected in series with its separately excited field By changing the setting of this rheostat the output voltage of the generator is changed, the mode of operation of such a generator in this respect being well known. For convenience in operation a volt meter ill is connected across the output leads 88, 8l of the generator so that the operator is continuously apprised of the voltage applied to the network. An auxiliary manually operated on-oi! switch Ill is preferably interposed in a circuit for the generator field Il so that it can be used at will to open-circuit this field and drop to zero the output voltage of the generator.

The means for varying the phase relation of the generator output voltage and current has been shown (Fig. 19) as comprising a variable condenser Ill connected in shunt with the transformer primary winding II. The inductive reactance of the transformer and the capacitive reactance of the condenser go to make up a tuned circuit, and by adjusting the capacity of the condenser the phase relation of the voltage and current can be changed at will. A similar variable condenser (not shown) is associated with each of the transformers for the various electrode sections. 'Ihis affords great flexibilityv of operation for the machine since the size of the holes produced by each of the sections can be varied independently by adjusting the condenser for such section. On the other hand if it is desired to make a simultaneous change in the size of the holes produced by all of the sections this can be effected' by changing the generator output voltage through the medium of the adjustable rheostat lli.

To afford the operator a visual indication of 'the condition of operation for the various sections of electrodes, a gaseous discharge tube such as a neon lamp I Il (Fig. 19) is connected in series with each of the transformer secondaries. One such lamp is provided for each of the nine transformers. The high order of magnitude of the output voltage from the transformers is sumcientl to render these tubes conductive but the voltage drop through them is very small and their current consumption is also small so that they do not materially diminish the emciency of the system. When full load current is flowing through ,threaded in the bell crank III,

assenso varied the intensity and color of the light emitted, by the pilot lamp changes accordingly. When the individual on-oi! switch I for any particular tubes section is opened the associated pilot tube is darkened, indicating that its section is out of service. The group of nine pilot tubes IIII may be conveniently mounted on a single panel (not shown) at any convenient point of control and the individual on-oif switch I is desirably mounted on the same panel adjacent the corresponding pilot tubes. Y

In many instances it is desirable to provide separate'driving means for rotating `the electrode rolls and for driving the high frequency generator. In auch case the driving means are desirably interlocked so that no potential will be applied to the electrodes unless the rolls are rotating at a speed exceeding a predetermined minimum. By providing such an interlock danger of badly charring or even burning the web Il by repeated discharges through the same portions of the web is obviated. To effect this interlocking the safety switch III (Fig. 19) is arranged to be actuated in response tc the speed of rotation of the rolls. As was heretofore noted, when this switch Ill is open. the relay |02 is dropped out and all supply of potential to the electrodes is thereby cut off. y

In the illustrative construction (Fig. 1) the switch IIII, which is a normally open so-called micro-switch. is mounted on the left end frame of the machine. This switch is provided with an upstanding actuating plunger II| (Fig. 17) which must be pushed down to close the switch. Pivoted on the end frame of the machine with one arm overlying-the plunger I Il is a bell crank I I I. This bell crank has a bifurcated lower end embracing the roll Il (see also Fig. 18). Keyed for axial movement on the roll is a collar H2 which is arranged to abut against the enlarged lower ends of the bell crank I Il. An annular weight or ring III is pivoted by trunnions III on the shaft I2 at a point axially displaced from the collar IIf. This ring I I3 is tiltable in a direction transverse to the shaft axis and is connected to the collar III through links III and IIl arranged on diametrically opposite sides of the roll If. The opposite ends of these links are pivotally connected respectively to the collar II! and to the ring III. In the case of the collar II! they are connected to it at diametrically opposite points, but in the case of the ring III they are pivoted to it at points eccentric to its trunnions III. Tension springs H1, anchored at their opposite ends to the shaft Il and to pivot pins III which connect the links to the ring, normally tilt the ring Ill to the position shown in full lines in Fig. 17. The links III, III are thus thrust endwise to the left and move the collar Il! to the full line position shown where it abuts against the bell crank III and swings it in a clockwise direction to release the switch plunger III. A tension spring I I9, anchored at one end of the machine frame and at its other end to a screw |20 adjustably serves to vary the cooking tension of the switch mechanism.

When the roll I2 is rotating, centrifugal force tends to swing the ring I II into a plane transverse to the axis of shaft rotation (position indicated in dot-dash lines in Fig. 17) Such movement is yieldably opposed by the tension springs I I1.

' When the speed of rotation for the roll I2 finaltension is overcome and the ring III is shifted to the dot-dash position in Fig. 1'1 whereupon the collar I is drawn to the right, thereby disengaging the bell crank lever so that the latter is pulled down'bythe spring Il! and the switch closed. Closure of this switch |0| (see Fig. 19) conditions the relay |02 for energization upon the subsequent closure by the main on-oif switch To vary the speed-responsive setting yof the switch-actuating mechanism the eiIective length of the links H6, H6 may be altered. For this purpose each of the links is made up of two overlapping portions one of which is longitudinallyy slotted as indicated at |2|. Screws |22 threaded in the other member and projecting through (the slot releasably clamp the link portions together. Adjustment of the tension in the spring ||9 also serves to effect smallerl or nner adjustments in the speed setting of the mechanism.

In Fig. 20 is shown a modified transformer circuit for one set of electrodes and which may 7 electrodes of the selected electrode sections. The rotation of the generally spiraled electrodes on the side rolls moves them so that the point thereon in closest proximity to the center roll electrode bands (and hence the point from which a spark will Jump to thecenter roll band since the spark travels through a path of'least distance) moves progressively along the spiral or zigzag electrodes. Thus as successive cycles of voltage are applied the sparks -occur at successively spaced points along the zigzag electrodes. To vary the spacing between these successive points,

l", the relation between frequency of the voltbe substituted for that of Fig. 19 to obtain even greater latitude in intensity of arcing between the electrodes and, hence, in perforation size. In general,` transformers 00* are arranged to sup plement the transformers 90 previously described. Each of the transformers 90'A is identical with the transformers 90 and includes a primary winding 9|. and secondari'es 92* and 03. The primary winding 9|a may, at will, be connected in parallel with the primary of the transformer 00, through an on-oif switch |04", so as to be supplied from the same generator 8|. Similarly, the secondaries are connected across the electrodes by a switch |04. When open these switches prevent feed-back to the circuit of the transformer 90. By cutting the supplemental transformer 00* into circuit the power applied tothe associated electrodes is practically doubled. Nevertheless, the condensers |09 and generator output voltage control can be used as before to vary the perforation size even with the supplemental transformers in circuit although the range through which the variations take place is correspondingly enlarged.

Brief rsum of operation Assuming that the leading portion of the web |0 has been threaded between the rolls as heretofore described, the operator preliminarily conditions the machine for operation by opening or closing various ones of the individual on-ofi switches |04, the ones closed depending upon the width of the sheet to be perforated and the den\ sity of distribution desired for the perforation pattern. If a very dense pattern of perforations on a sheet of maximum width is desired, all of the switches |04 are closed so that all of the sections of electrodes will be operative. Additionally the generator driving motor I4 is started and the output voltage for the generator checked on the meter |01, any desired variations in such voltage being effected by adjusting the rheostat |06.

With the machine preliminarily conditioned as described, the main on-ofl' switch |00 may be y vhage and speed of web advance can be changed.

This can be done either by changing the frequency, through variation in speed of the generator driving motor 04, or by changing the speed of web advance by change in speed of roll rotation, or both.

To vary the size of the' punctures in the web I0 formed by the discharges in any selected section of electrodes, the corresponding variable condenser |08 is adjusted. By changing its setting the phase relation of the voltage and current is altered, as heretofore explained, so that the power expended in the discharges is correspondingly changed.

In the event that the operator wishes to change simultaneously the size of the perforations formed by all of the electrode sections he changes the output voltage of the high frequency generator 8|. To do this he varies the excitation of its field 0! by means of the rheostat I".

If the modified circuit of Fig. 20 is used the range of perforation size may be further increased by closing switches |04* and |00b to cut in the supplemental transformer 90* for a selected section of the machine. Thereafter the controls |00 and |08 are used as described above to vary the output of the now parallel connected transformers 90 and 00.

In the event that the roll driving mechanism should become stalled or the rolls stopped for any other reason the web |0 is completely protected against burning. Any such stoppage of the rolls automatically opens the safety switch |0| and thereby prevents further application of voltage to the electrodes.

From the foregoing it will be apparent that a remarkably versatile machine has been provided. Adjustment of the clearance between the rolls makes it possible to accommodate a wide variety of thicknesses of sheet material. This also aids to some extent in conditioning the machine for different kinds of material while the complete nature of the control over arc power makes it possible to obtain a desired size of perforation despite differences in the dielectric qualities of the particular materials. Coupled with this is the ability to obtain a uniform pattern of distribution for the perforations and one which is of selectively variable density. In view of this completeness and flexibility of control an extremely wide variety of materials can be handled effectually and at extremely high speeds.

We claim as our invention:

1. The method of pattern perforating a sheet of material which comprises passing electrical arc discharges through the sheet at spaced points along predetermined intersecting lines. and varying the number of such lines criss-crossing each other in unit areas of the sheet to vary corre- I spondingly the density of the pattern of perforations. l

2. The method of pattern perforating a sheet of material which comprises passing electrical arc discharges through the sheet at successive spaced points along a plurality of zigzag lines with such lines successively overlapping the same portions ofthe sheet and arranged with certain of such lines oiTset with respect to each other laterally oi' the sheet and also with certain of said lines staggered with respect to each other longitudinally of the sheet.

3. The method of periorating a sheet which comprises locating the sheet between a plurality oi pairs of electrodes, applying potential between said pairs ci electrodes from a common source ot potential to establish periodical arc discharges between such electrodes and thereby puncture the sheet, varying the output potential of said source to .change correspondingly and simultaneously the size oi' the punctures produced by all of such discharges, and varying the phase relation between the potential. and current supplied to selected ones of the pairs of electrodes to change independently the size ci' the punctures produced by the discharges between the selected pair or pairs of electrodes.

4. In a sheet perforating machine. the combination of power actuated means for advancing a web, a set of electrodes comprising a plurality of zigzag electrodes and cooperating electrodes spaced from the former and arranged with each zigzag electrode on the opposite side o! the path oi' web advance from its cooperating electrode. means for causing electrical arc discharges to pass between the zigzag electrodes and corresponding ones of the spaced electrodes at spaced points along selected ones of the zigzag electrodes, and said zigzag electrodes being offset with respect to each other in a direction transverse to the path of web travel.

5. A machine of the type set iorth comprising, in combination, rst and second rows of electrodes arranged in parallel spaced relation; a third row of cross-over electrodes between said tlrst and second rows disposed in closely spaced relation to the latter to receive in the resulting gaps between the iirst and third rows as well as the second and third rows portions of sheet material to be perforated; means electrically interconnecting predetermined ones of the electrodes in the second row which are so positioned with respect to those in the ilrst row as to form a series circuit including in the order named an electrode in the nrst row, a cross-over electrode, two series connected electrodes in the third row, a second cross-over electrode and a second electrode in the rst row; and means for applying a periodically varying electrical potential to the terminals of said series circuit to set up arc dis- {charges in said gaps and through the portions of sheet material between successive electrodes in said series circuit.

6. A sheet perforating machine comprising, in combination, a center roll and a pair of parallel side rolls disposed on generally diametrically opposite sides of said center roll, said rolls being spaced apart to receive a traveling web passing through the gaps thus formed between the center roll and respective ones of the side rolls, said center roll having an electrode thereon in the form of an annular conductor encircling the same, each of said side rolls having an electrode thereon comprising a zigzag annular conductor encircling the respective roll and opposed to the electrode on the center roll, and means for periodically applying a potential between the side roll electrodes to cause an electric impulse to passiromonesiderollelectrodethromhthecem terrolleleetrodetothsothersiderollelectrcde, theresultingarcdischargesinthegapsseparatingthesiderollsandthecenterrcllservingtel "zigzag electrodes on the roll to receives web therebetween which is to be perforated, and meansfcrapplyinsanelectricalpotentiaibetween the roll supported electrodes and said cooperating electrode structure, said las; named means includingaslipringconnectinntor'thsrollm' ported electrodes.

8. A sheet perforating machine comprising, in combination, a pair of parallel side rolls disposed on opposite sides ot a centrally located crcu-over v electrode, said rolls being spaced from the center electrode to receive a traveling web passing through the gaps thus formed between theeenter electrode and respective ones of the side rolls, each of said side rolls having an electrode thereon comprising a zigzag annular conductor encircling the respective roll and opposed to the center electrode. means tor periodically applying a potential between the side .roll electrodes to cause anelectricimpulsetopassi'romcnesidoroll electrode through the center cross-over electrode to the other side roll electrode. the resulting are discharges in the gaps separating the side rolls and the center electrode serving to puncture the web at such points, power actuated means los' rotating said side rolls in unison andthe zigzag side roll electrodes being onset from each other inanangularsensesbcuttheaxesoftheirrespective rolls.

9. In a sheet periorating machine, the combination of a plurality o! pairs o! spaced electrodes adapted to receive a traveling web between the successive pairs. at least one electrode in each pair comprising a dans annulus of conducting material, power actuated means for rotating the zigzag annular electrodes in unison to bring successive points along the same into proximity with the other electrode in each pair, means for applying potential periodically between the electrodes in each pair to cause arc discharges to pass between the points o! closest'proximity in each pair and through the web, and said zigzag annular electrodes being odset from each other in an angular sense about their respective axes of rotation.

10. In a sheet pertorating machine, the combination of a plurality oi' pairs oi' spaced electrodes adapted to receive a traveling web between the successive pairs, at least one electrode in each pair comprising a zigzag annulus of conducting material, power actuated means for rotating the zigzag annular electrodes in unison to bring successive points along the same into proximity with the other electrode in each pair, means for applying potential periodically between the electrodes in each pair to cause arc discharges to pass between the points of closest proximity in each pair and through the web, and said zigzag electrodes being oilset with respect to each other not only laterally of the path of web travel but also in an'lngular sense about their respective axes of rotation.

11. A sheet periorating machine comprising.

in combination, a plurality of sets of revoluble rolls, each oi said sets including a center roll and a pair of parallel side rolls disposed on generally diametrically opposite sides of the respective center rolls, the rolls in each set being spaced apart to receive a traveling web passing through the gaps between the center roll in each set and the respective side rolls in the set, each of said center rolls having an electrode thereon in the form of an annular conductor encircling the same, each of said side rolls having an electrode thereon comprising a zigzag annular conductor encircling the respective roll and opposed to the electrode on the associated center roll,

means for periodically applying a potential between the side roll electrodes in each set to cause an electric impulse to pass from one side roll electrode in each set through the center roll electrode for such set to the other side roll electrode of the set, the resulting arc discharges in the gaps separating the side rolls and respective center rolls serving to puncture the web at such points, and said side roll electrodes in each set being offset in a direction longitudinal of the rolls with respect to the side roll electrodes in the other sets.

12. A sheet perforating machine comprising, in combination, a plurality o! sets of revoluble rolls, each of said sets including a center roll and a pair oi.' parallel side rolls disposed on generally diametrically opposite sides of the respective center rolls, the corresponding rolls in the various sets being arranged in alinement and the rolls in each set being spaced apart to receive a traveling web passing through the gaps thus formed between the center rolls and the associated side rolls, each of said rolls having an electrode thereon, means for applying an electrical potentialto the side rolls in Aeach set to cause an electric impulse to pass from one side roll in each set through the associated center roll electrode to the other side roll electrode in the set, and adjusting means for simultaneously shifting all of the side rolls located on one side of their respective center rolls and in alinement with each other toward or away from the center rolls to adjust the lengths of the gaps therebetween.

13. In a machine of the type set forth, the combination of three rolls having peripherally located electrodes thereon, means revolubly supporting said rolls in parallel spaced relation to form air gaps between said electrodes through which a web to be perforated may be led, means for applying an electric potential between the electrodes on two of the rolls to cause series arcsy in the gaps between such electrodes and that on the other roll, and means for adjusting the spacing of said rolls to vary the lengths of the air gaps through which the series arcs pass.

14. In a machine oi the type set forth, the combination of a revolubly mounted insulating member having a cylindrical exterior surface, an annular electrically conductive metal bar oi' zigzag form encircling said member and having laterally projecting integral feet resting on the exterior of said member, and means including segments of insulating material overlying said feet for xing the conductor to said member to form an electrode encircling the same.

15. A machine for perforating a moving web comprising, in combination, a plurality of parallel revoluble rolls arranged to have a moving web threaded between them, a plurality of electrodes distributed along at least one of said rolls at points spaced longitudinally of the latter, a cooperating electrode structure on another of the rolls lying on the opposite side of the path of web travel from said one roll, a power source for supplying a periodically nuctuating potential, and means operable at will to connect selected criesv oi' said electrodes on said one roll in circuit with said power source to energize a plurallty of said electrodes extending a distance along said one roll commensurate with the width of the web.

16. In a, sheet material perforating machine, the combination of a plurality oi' sets of electrodes arranged to receive a sheet between them. means for applying potential periodically to a pair of electrodes in each set to pass an arc discharge between the same and through the sheet to peri'orate the latter, means for varying individually the power expended in the arcs in selected ones of said sets of electrodes, and means for varying simultaneously the power expended in the arcs in all of said sets of electrodes.

1'1. In a sheet material perforating machine, the combination o! a plurality of sets of electrodes arranged to receive a sheet between them. means for applying potential periodically to a pair of electrodes in each set to Pass an arc discharge between the same and through the sheet to perforate the latter, means for varying individually the power expended'in the arcs in selected ones of said sets of electrodes to establish a selected differential relation for expenditure of power in the variousl sets of electrodes, and means operable independently of the setting of said rst named control means and without disturbing the differential relation set up between the various sets of electrodes by said first named control means i'or varying simultaneously the power expended in the arcs in all of said sets of electrodes.

18. In a sheet material perforating machine, the combination of a plurality of sets ot electrodes arranged to receive a sheet between them, means for applying potential periodically to a pair of electrodes in each set to Dass an arc discharge between the same and through the sheet to perforate the latter, means for varying individually the power expended in the arcs in selected ones of said sets of electrodes, and means for varying the potential supplied tb said sets of electrodes to vary simultaneously the size of the punctures produced in the sheet by all of said arcs.

19. In a sheet material perforating machine, the combination of a plurality of sets of electrodes arranged to receive a sheet between them. means for applying an alternating current potential to a pair of'electrodes in each set to pass arc discharges between the same and through the sheet to periorate the latter, means for selectively varying the phase relation between the voltage and currenty supplied to selected ones of said sets of electrodes, and means for varying simultaneously the potential supplied by said power source to all of said sets of electrodes.

20. In a sheet material perforating machine, the combination of a pair of electrodes adapted to receive between them a sheet to be perforated, means for supplying high frequency alternating current, means for connecting the supply means to said electrodes to cause arc discharges to Pass between the electrodes and puncture the sheet. said `connecting means including two step up transformers having input and output circuits connected in parallel relation to each other retrodes, and switching means'tor alternatively cutting in or out oi' circuit one of said transformers to vary the power output to the electrodes.

21. In a. machine for pertorating a traveling web, the combination of a plurality ot revoluble rolls arranged for the web to be led between them and about at least one of the rolls in frictional contact with the latter to advance the web upon rotation of said one roll, power actuated means for rotating said rolls in unison. at least some of said rolls having electrodes on the peripheries thereof, means lor applying potential to the electrodes to pass arc discharges therebetween and through the web, and means including a. safety interlOck switch actuated in response to the speed of rotation oi' said rolls for preventing the application of potential to assigne saidelsetmdesbythelastmentlonedmeans emptvhentherolisarerotatingataspeed inexoessotapredetermined minimun.

Illethod of periurating sheet material whicheonsistsinimpaxtingmovamenttoths sheetinthedirectionoloneotitsareadimensions while causing a multiplicity ot electric arostosimultaneouslypieraseriesofvertorationsinthesheetextendinginalineacross the sheet transversely to the direction ot movement of the same wlmreby perforation are formed over an ares of the sheet two. dimensionaily andcontrollingtbespacing ottheperiorationsinthedirectionolthemovementoithe sheetbyvaryingthetreqncyotthediseharges reiativeiytothespeedatwhichthesheetis moved IRVIN H. WILBIY, AR'IHURI. NIUKANN. 

